The invention relates to a twisting nozzle used as a processing aid in the manufacture of multi-filament yarn. More particularly, the invention concerns a system that includes processes and equipment for improving the uniformity of yarn finish application on the individual filaments of rapidly advancing yarn by utilizing a pneumatic false twister.
A conventional method disclosed in U.S. Pat. No. 3,201,931 separates yarns having continuous fibers in order to bulk the yarn by feeding the yarn into a jet of air, so that the yarn is supported by the jet of air and the individual filaments are separated from each other. The separated individual fibers are thus passed through a turbulent area where intermingling and texturing occurs. The bulked yarn is then passed through a dye bath.
A process of twisting of filaments into a cohesive single yarn entity is disclosed in U.S. Pat. No. 3,534,453, where the resultant yarn bundle is textured via pneumatic means and atomized dye stuffs are introduced via the sonic or subsonic fluid flows before the yarn bundle is completely closed by the twisting action of the flow currents. The thread enters the interior of a nozzle and a stream of pressurized air enters a xe2x80x98heart-shapedxe2x80x99 xe2x80x9cbulbxe2x80x9d or annulus through a duct. The position of the duct relative to the nozzle axis produces the familiar effect of the required amount of twisting, fixing, and untwisting. A xe2x80x9ctrue twistxe2x80x9d of the yarn bundle is a result of this process, and the manifestation of false twist xe2x80x9cSxe2x80x9d or xe2x80x9cZxe2x80x9d patterns in individual discrete filaments in the resultant processed yarns is due to either direct contact with the chamber wall or the interactions of subsonic and sonic pneumatic flows within the nozzle chamber on the plurality of fibers.
A method for opening and applying finishes to multifilament tows is disclosed in U.S. Pat. No. 3,226,773, in which a compressed air stream is used for spreading and separating the filaments of a tow bundle and for carrying the particles, droplets, or mist of the finish composition to be applied to the filaments. In actual practice, the oscillation of the advancing tow bundle within the nozzle chamber creates momentary flow disturbances in the plenum chamber and supply metering orifice that alter the concentrations of entrained atomized finish particles. Sufficient filament displacement occurs within the advancing tow bundle for it to be described as xe2x80x9cfleecy,xe2x80x9d intermingling and interlacing thereby occuring.
The invention relates to a finish application system that uses several variations of air nozzles that are somewhat similar to conventional interlacers/interminglers, but have completely different functions. Conventional interlacers/interminglers operate at relatively high pressures (up to 4 bars) and are designed to provide additional cohesion to the filament yarn by creating so-called nodes or loose knots. The conventional devices are designed to work at very low tensions and are not suitable for finish application.
The invention relates to the application of yarn finishes, such as those containing lubricants and/or other additives, to the advancing filaments within the converged yarn bundle in state-of-the-art high speed extrusion processes for yarns formed of man-made and/or natural polymeric materials. These processes have reached speed ranges of as much as 3000-8000 meters per minute, where the extrusion tension levels and the residence times on the conventional wetted type applicator surfaces preclude a high degree of uniform and consistent capillary action on the individual filaments within the yarn bundle. This can be attributed to several causes: the entrained boundary layer of cooling air flow that each filament brings to the applicator; the residual retraction forces associated with filament tension that are still remaining in the filaments within the advancing yarn bundle due to the drawing process; the apparent viscosity phenomena associated with the high speed contact of the filaments within the advancing yarn bundle with the pool of yarn finish containing lubricants, and/or other additives on the wetted applicator surface; and, due to the applicator""s ability to renew the pool of finish under the yarn bundle contact zone.
In order to reduce these and other conventional problems associated with uniformity of finish application, it is an object of the present invention to dissipate the entrained boundary of air, steam, inert gas, or other types of cooling or heating fluids that inhibit the uptake of the yarn finish containing lubricants or other additives on the advancing yarn bundle prior to the entrance of the yarn bundle into a nozzle device.
It is an additional object of the present invention to disturb the linear interfilament cohesion within the advancing fiber bundle that inhibits the attachment of yarn finish through capillary action without also creating noticable sinusoidal and or nodal mixing patterns (known as xe2x80x9cinterminglingxe2x80x9d or xe2x80x9cinterlacingxe2x80x9d patterns) in the advancing yarn fiber bundle that could inhibit downstream processing techniques.
It is a further object of the present invention to introduce yarn finish containing lubricants, or other additives, into an applicator chamber that provides for low pressure contact of the individual filaments with the wetted surfaces of the applicator chamber and with the atomized fluid volume within the nozzle chamber.
It is another object of the present invention to provide a low pressure nozzle chamber that dampens pressure and volumetric irregularities in the introduction of the yarn finish into the applicator chamber.
Yet another object of the present invention is to immediately close the opened filaments of the advancing fiber bundle containing the yarn finish immediately after passing the nozzle, in order to aid in the prevention of the previously applied finish being stripped off by the reattachment of the boundary layer air, after the yarn passes through the nozzle.
Still another object of the present invention is to provide a type of air bearing yarn filament support medium within the applicator chamber, to inhibit the escalation of tension in the advancing yarn line normally associated with direct fiber filament contact with the application surface.
An additional object of the present invention is to introduce more surfaces of the advancing filament bundle cross sections to the wetted surfaces of the applicator and to the atomized finish particles within the nozzle chamber.
Another object of the present invention is to allow the applicator to renew with finish the application surfaces of the applicator, in order to facilitate the uniform and consistent presentation of the finishes to the advancing yarn line.
Another object of the present invention is to reduce the friction and the friction buildup of the yarn within the nozzle chambers, so that the moving yarn may be opened or closed under high tension, allowing the nozzle to act as an air bearing.
Different air pressures can be used to operate the pneumatic false twister. Low pressure (up to 2 bars) air nozzles can be used for the application of yarn finish processing aid components. The Advanced Finish Nozzle (AFN) of the present invention contains compressed air delivery orifices that are used to effect the false twisting and untwisting of the yarn within the nozzle. When air pressure is applied to the AFN, the yarn filaments remain twisted together, and when no air pressure is applied to the AFN the yarn remains untwisted. The AFN is capable of opening and closing of multi-filament yarn at high tensions (up to 1.0 gram per denier) by the application of a xe2x80x9cS/Zxe2x80x9d semi-twist, or false twist, to the moving yarn. The AFN is also designed to apply finish onto the moving yarn while xe2x80x9copenxe2x80x9d inside of the nozzle. The nozzle can be used immediately after a conventional application of a liquid finish to the multifilament yarn, or can contain additional orifices that are used to spray the finish onto the yarn while the yarn has been opened by the nozzle and before the yarn closes into its normal state. This action allows for extremely uniform finish application especially in situations where some additional amount of finish has to be applied on already spun and drawn (or even heat set) yarns.
The nozzle is designed so that an air bearing curtain (e.g., helix) is provided surrounding the advancing threadline to cause an orbital dislocation , thereby separating and opening the yarn bundle. A convergence of the thread can occur within or just after passing the nozzle.
The AFN does not use the atomizing of particles of finish for reasons of system complexity and overall variability of finish concentrations. The AFN requires the delivery of a metered stream of yarn finish directly into the yarn processing chamber and thereby improves over conventional systems such as the above-mentioned U.S. Pat. No. 3,226,773.
The manifestation of the xe2x80x9cSxe2x80x9d or xe2x80x9cZxe2x80x9d twist patterns in the filaments of the advancing yarn bundle in the AFN is the result of individual filaments within the advancing yarn bundle accepting rotational torque and radial bundle displacement from the helical discharge path of the perimeter air currents within the nozzle chamber. The algebraic sum of this twist is zero when measured over a certain length of the yarn bundle.